A number of expansion joint systems are known in the prior art. These systems are used between two slabs of relatively rigid material such as concrete. The slot enables the slabs to move relative to one another. Relative movement may occur both in the vertical and horizontal directions due to factors such as thermal expansion, settling or relative loading. Expansion joint systems are commonly used in bridges, walkways, parking structures, roadways and in other structures that are used to carry vehicle or pedestrian traffic.
Expansion joints typically serve to maintain a continuous surface above the slot between the slabs. Expansion joint systems also typically aid in preventing water and other contaminants from getting into the slot where they may damage the joint or the adjacent slabs. Problems may occur with various types of prior art expansion joint systems when the slabs move further apart than the expansion capability of the system. This causes the joint to fail due to rupture or separation from the slabs. In other circumstances the slabs may move together, compressing the joint to the point that it is destroyed or disengages from the slabs. Most expansion joints also undergo repeated cycles of expansion and contraction. This repeated cycling of the joint system may cause the joint to fail due to fatigue. Also, expansion joint system components are subjected to dirt and other contaminants which may attack the materials and cause premature failures.
Expansion joint systems known in the prior art are prone to failure in cold weather. Impacts from traffic or snow plows moving over the joint may cause the joint to tear or separate from the adjacent slabs.
The failure of expansion joint systems is particularly problematic in areas where the system experiences shear or where there is large differential deflection between adjacent slabs due to loading or thermal expansion. Particularly difficult applications for expansion joint systems include the joints between the concrete slabs that comprise parking structures, plaza decks and pedestrian bridges.
Thus, there exists a need for an expansion joint system that is more reliable, has greater expansion and contraction capability and is more shock and fatigue resistant than prior art expansion joint systems.